craft sector, to survive, pays unskilled labor meagerly.* These evidences of change in the personal distribution of income give assurance that rates of return to basic education in the low income countries today are substantial and may be increasing. This situation gives parents an added incentive for furthering the education of their children. As emphasized earlier, parents may view differently these opportunities for investment in their children's future, depending upon their own consumption needs, alternative investment opportunities, and their attitudes toward the family's future. Uncertainty and Change in Birth Control Technology Recent developments have also changed the environment in which parents reach their reproductive goals. Three basic sources of uncertainty enter into their supply of children: (a) death may take the lives of more or less of their children than they anticipate; (b) parents may not be able to bear the number (and sex distribution) of children they want; and (c) parents may bear more children than they want. As discussed earlier, improved chances of child survival have markedly narrowed the range of uncertainty a parent must cope with in forming his family. Hedging against catastrophic family losses has become less pressing. To some degree, advances in reproductive biology and improved institutions of adoption may have also reduced the prevalence of sterility or alleviated its impact on family planning. However, the most important change has taken place in the technology of birth control and the administration of health and family planning programs. The costs of birth control, pecuniary and nonpecuniary, are much more than the money outlays and the inconvenience associated with using a method; they also consist of the task of acquiring and evaluating information about alternative methods. This task may represent an insurmountable obstacle to the natural diffusion of new techniques in a low income, poorly educated country. However, new techniques of birth control provide for highly reliable regulation of fertility at little cost or inconvenience, while family planning programs have improved methods of disseminating these ideas and services to all strata of society. Among the lower social and economic classes of the less developed world, particularly the costs of evaluating, adopting, and using modern birth control are decreasing sharply. Where there is already demand for averting births, this reduction in birth control costs should be reflected in more rapid and humane reductions in fertility.t Many more factors which are linked to the development process in low income countries could be discussed; some might foster and others retard the long-term trends in parents' demand for children.^ The changes stressed here *See(33,Ch.V;31,32). tsce(33,Ch.VHI;3).